Electrocatalytic water-splitting has gained a firm hold in the area of renewable hydrogen production owing to its integrative compatibility with intermittent energy sources. However, wide-scale implementation of this technology demands discovery of new electrode materials that strike a good balance between efficiency, stability, and cost. In the pool of inexpensive electrodes capable of catalyzing hydrogen and oxygen evolution reactions, metal borides/ borates have made a big splash in the last decade. However, the research in this family of electrocatalysts remains unorganized owing to the diversity of reports. This review summarizes the past and present research progress in metal borides/borates for electrocatalytic water-splitting. The fundamental reasons for electrochemical behavior in different metal borides/borates are highlighted here, also including some comments regarding erroneous practices in the performance evaluation of metal borides/borates. Various strategies used to enhance the electrocatalytic performance of metal borides/borates are discussed in detail. Different methods evolved over the years for the synthesis of metal borides/ borates are also discussed. Finally, an assessment of the commercial viability of metal borides/borates is made and future research directions are suggested. multimetal oxides, [18,19] layered double hydroxides, [20] oxyhydroxides, [21] and perovskites. [13,18] In addition to these, there has been the family of transition-metal borides/borates that have garnered enormous interest in the recent past. Though transition-metal borides (TMBs) have been used for water electrolysis since many decades, they were not really seen as potential candidates to replace noble metal catalysts, until recently. Indeed, in 2009, the group of Daniel Nocera reported in situ formed Co [22] and Ni [23] borates as analogous catalysts to Co phosphate, [24] for near-neutral water-splitting. Later, the groups of Hu [25] and Patel [26] reported development of Mo boride and Co boride, respectively, for electrocatalytic water splitting. Following these reports, transition-metal borides/ borates [27][28][29][30][31][32] were developed using various techniques and were used extensively for water-splitting reactions, in different pH solutions. Here, we would like to inform the readers that usually boron-based catalysts that are developed in situ using electrodeposition are referred to as "borates" (denoted as M-B i , M = metal) while those catalysts prepared by any other technique are referred to as "borides" (denoted as M-B). Over the past 5-6 years, a lot of studies have been carried out on borides/borates with remarkable results, presenting new possibilities in search for non-noble electrocatalysts. The electrochemical performance, stability and other important properties of all the metal borides reported so far are enlisted in Table 1 while that of metal borates are listed in Table 2. However, there are a lot of aspects that are not yet understood completely about borides/borates. For instance, the o...

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The family of layered carbides and nitrides known as MAX phase ceramics combine many attractive properties of both ceramics and metals due to their nanolaminate crystal structure and are promising potential candidates for application in future nuclear reactors. This investigation examines the effects of energetic heavy ion (5.8 MeV Ni) irradiations on polycrystalline samples of Ti3SiC2, Ti3AlC2, and Ti2AlC. The irradiation conditions consisted of midrange ion doses between 10 and 30 displacements per atom at temperatures of 400 and 700 C, conditions relevant to application in future nuclear reactors and a relatively un-explored regime for this new class of materials. Following irradiation, a comprehensive analysis of radiation response properties was compiled using grazing incidence X-ray diffraction (XRD), nanoindentation, scanning electron microcopy (SEM), and transmission electron microscopy (TEM). In all cases, XRD and TEM analyses confirm the materials remain fully crystalline although the intense atomic collisions induce significant damage and disorder into the layered crystalline lattice. Xray diffraction and nanoindentation show this damage is manifest in anisotropic swelling and hardening at all conditions and in all materials, with the aluminum based MAX phase exhibiting significantly more damage than their silicon counterpart. In all three materials there is little damage dependence on dose, suggesting saturation of radiation damage at levels below 10 displacements per atom, and significantly less retained damage at higher temperatures, suggesting radiation defect annealing. SEM surface analysis showed significant grain boundary cracking and loss of damage tolerance properties in the aluminum-based MAX phase irradiated at 400 C, but not in the silicon counterpart. TEM analysis of select samples suggest that interstitials are highly mobile while vacancies are immobile and that all three materials are in the so-called point defect swelling regime between 400 and 700 C. All results are consistent with previous work involving traditional and MAX phase ceramics. Results show that the aluminum MAX phases are not fit for application near 400 C and that the silicon MAX phase is overall more damage tolerant.

Organic–inorganic perovskites have emerged as an important class of next generation solar cells due to their remarkable low cost, band gap, and sub-900 nm absorption onset.

Ion irradiation experiments and atomistic simulations were used to demonstrate that irradiation-induced lattice swelling in a complex oxide, Lu2Ti2O7, is due initially to the formation of cation antisite defects. X-ray diffraction revealed that cation antisite formation correlates directly with lattice swelling and indicates that the volume per antisite pair is approximately 12  Å3. First principles calculations revealed that lattice swelling is best explained by cation antisite defects. Temperature accelerated dynamics simulations indicate that cation Frenkel defects are metastable and decay to form antisite defects.

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With a motivation to discover efficient materials for direct electrolysis of seawater, bimetallic oxy-boride (Co−Fe−O− B) nanostructures were developed using a facile hydrothermal synthesis strategy, with varying content of Fe. The oxygen evolution performance of the optimized Co−Fe−O−B catalyst in alkali water (1 M KOH) showed higher reaction rates owing to a Co 3 O 4 −core−Co 2 B-shell structure, which assists in the formation of active CoOOH species at lower potentials and offers a smaller charge-transfer resistance. The best-performing catalyst in alkali water was found to be highly active (294 mV to achieve 10 mA/ cm 2 ) in saline water (1 M KOH + 0.5 M NaCl), with 100% O 2 selectivity, establishing its potential for seawater electrolysis. The high activity and selectivity of the oxy-boride catalyst in alkaline saline electrolyte presents a fresh avenue for research in low-cost materials, especially boron-containing compounds, for selective seawater splitting.